Electric switch



Aug. 13,1929.

E. E. F. CREIGHTON ELECTRIC SWITCH Filed Feb. 21, 1924 Inventor: v Elmer ET Crl ighton, y 26" His Attorney.

Patented Aug. 13, 19 29.

UNITED STATES PATENT ori -"ice.

ELMEB E. F. CREIGHTON, OI SGHENECT ADY, HEEV YORK, ASSIGNOR' TO GENERAL I ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ELECTRIC SWITCH.

Application filed February 21, 1924. Serial No. 694,405.

My invention relates to electric switches of the fluid break type and particularly to those ich are employed for interrupting circuits of comparatively high voltage.

When the contacts of such a switch are separated beneath the surface of the insulating fluid to open the circuit, the are drawn immediately volatilizes and dissociates a part of the fluid forming a bubble of highly heated gas extending between the separated contacts. In fluid break switches heretofore constructed it has been customary to confine the contacts and fluid together with the gas generated in a strong receptacle or tank. An object of my invention, however, is to provide an arrangement wherein the gas forming the bubble may find a comparatively free escape and wherein the initial resistance. met by the gas bubble is reduced and may be varied, thus reducin 'the size and pressure of the bubble and "hastening the ultimate rupture of the arc.

It is well known that as a bubble increases in size its cooling surface increases less rapidly than its volume, from which it follows that in a bubble of small size the surface is more eflicacious in cooling the contents than in a large bubble. According to my irivention I provide tubes which extend down through the'insulating fluid with their lower open ends adjacent the are drawn between the switch contacts. The uppcr ends of the tubes are provided with relief valves and beneath the valves the tubes are connected with a source of gas pressure suiticient to hold the fiuid'level in the tubes at or near their lower open ends. arrangement the gas formed at the contacts may escape up the tubes with comparative freedom, the bubble thereby remaining bushing 5, through which bushing extends a contact rod 6. Suitable mechanism, not

\Vith this.

ing the rod 6 into and out of contact with a stationary contact 7. Projecting through and secured to the cover et are shown the two tubes 8 of insulating material. The tubes are inclined to bring their lower open ends close to the switch contacts. the adjacent edges of the tubes being preferably cut away as shown. At its upper end each tube is provided with a metallic section 9 which has a number of openings 10 therein and just below these openings is a valve 11, Fig. 2, normally retained upon its seat 12 by a light coil spring 13. Suitable means are shown for adjusting this spring 13 comprising a screw 14 threaded into a cap 15 which may be screwthreaded on the end of the metallic section ofthe tube. Below the valve seat 12. of each tube a pipe 17 connects therewith, which pipe leads to a reservoir 18 which is filled preferably with a gas free from oxygen. Suitable means obviously may be employed to retain the proper pressure in the reservoir. The pressure of the gas in the reservoir need be only that suiticient to force the liquid level in the tubes 8 down to the desired level and the pressure exerted by the spring 13 should be only sufficient to hold the valves on their seats against this pressure.

hen the contacts 6 and 7 are separated to open the circuit the are drawn between the contacts volatilizes'or dissociates a certain amountof the insulating fluid producing a bubble of hot gas. As this gas formin; process is exceedingly rapid the gas bubble naturally rapidly increases in s1ze 1n spite of the inertia of the surrounding liquidlj The valve retaining springs 13 being relatively weak and the tubes being substantially full of gas whose inertia ascompared with the liquid is negligible,'the tubes offer a substantially free path of escape for the gas of the bubble with the result that the gas bubble remains small notwithstanding the rapid generation of gas by the arc. By reason of the small size of the bubble therefore and the resultant greater relative cooling effect of its surface, the arc is more rapidly cooled and more easily extinguished ruptin'gfa. heavy .durr'enti" By varying the pressure supplied? by the tank 18 the height ",lQ' ofthe liquid j'columnjin the tubes8 maybe varied to thereby. best adapt the switch to.

meet particular conditions, and because of this differential pressurefeature the station- 7 fary'contact may be covered toa considerable 1 depth by the insulating liquid, et the mass of liquid whichmust-be displaced to permit the ready escape: of the arc gases is relativelyfsmall and the specific surface or cooling surface-per unitvolume of the gas bub-. 2 ble between the contacts is accordingly larger than would otherwise-be the case.

Having thus described one embodiment of "my invention I do not wish to be limited to 1 the l particular form shown and described 2 as it will be apparent that .many modifications therein may be made without departing from the scope of my invention as set forth in the appended, claims.

What I claim as new and-desire to secure Q by Letters Patent of the United States, is

- 1. An electric switch comprising relatively movable contacts immersed, in. an insulating liquid and adapted when separated to draw an arc therein, and means for providing a substantially unimpeded path of escape through said liquid for the gas generated by said are independent of the depth of insulating liquid over said contacts.

=2. An electric switch comprising relatively movable contacts immersed in an insulating liquid and adapted to be. searated therein, thereby drawing an arc an formmg a gas' bubble, and vmeans comprising a tubular memberproviding' a substantially unimpeded path of escape through said liquid for'the gas of said bubble and means for maintaining the liquid level in the tubu- J lar member adjacent the lower' end thereof."

3. In an electric switch having cooperatmg relatively movable contacts immersed in an insulating liquid and adapted when separated to draw an arc, therein, means for freelyv conducting away the gas as it is formed at said are comprising a tubular member extending from said contacts to the surface of said liquid, and means for maintaining the liquid in said tube at a level mzlgterially lower than that outsidevo'f the tu e.

An electric switch comprisinga closed receptacle containing an insulating liquid, relatively movable switch contacts mounted in said receptacle beneath the surface of said liquid and adapted when separated to draw an ate, a tube extending into said receptacle and liquid to a point adjacent said contacts and means for normally maintaining that portion of said tube belt'vwthe level of said liquid substantially full of -gas.

5, An electric switch comprising a closed receptacle containing an insulating liquid, relatively movable switch contacts mounted in said receptacle beneath the surface of said liquid and adapted when separated to draw an are, a tube substantially full of gas extending into said receptacle and through said liquid to a, point adjacent said contacts, the pressure of gas in said tube being sufficient to expel substantially all of the llquid therein, and a resiliently closed valve at the upper end of said tube adapted to retain a the gas in said tube normally but to open automatically upon an excess of pressure therein. I

6. An electric switch comprising a closed receptacle containing an insulating liquid,- relatively movable switch contacts mounted in said receptacle beneath the surface of said liquid and adapted when separated to draw an are, a tube carried by and extending through the top of said receptacle, the lower open end of said tube being adjacent the arc drawn between said contacts, a spring pressed valve normally closing the upper end of. said tube, and a reservoir connected with said tube containin a pressure of a non-inflammable gas su cient'to maintain the insulating liquid-substantially displaced from the tube.

\ 7.- An electric switch comprisin -cooper-- 1 atingrelatively movable contacts lmmersed in an insulating liquid and adapted when separated to draw. an arc therein forming a gas bubble and means for variably limiting the pressure in said gas bubble at the initial formation thereof, said means comprising a gas filled tubular discharge" member having an adjustable spring pressed valve therein. In witness whereof, I have hereunto set my hand this 19th day of February, 1924.

ELMEB E. F. CREIGIITON. 

